This project will use the behavior of alveolar macrophages in tissue culture as a model to investigate local macrophage proliferation and differentiation in response to inflammatory stimuli. We will attempt to identify and characterize those cells of the macrophage series in the alveoli with the capacity for sustained proliferation, to measure the size of the alveolar pool of macrophage precursors (colony forming cells) in normal animals and in animals exposed to inflammatory stimuli and to investigate the possibility that short-range humoral factors (colony stimulating factors) are produced by lung cells which can stimulate macrophage proliferation. The effects of particulates, air pollutants and Freunds adjuvant on both the number of colony forming cells and on the production of the colony stimulating factor will be studied as models of inflammation. Colony forming cells will be separated from alveolar lavage and characterized with respect to morphology, cytochemical enzyme activities, phagocytic capacity, and membrane receptors.